Study: Forest patch treatments help protect older trees

A three-year study in Washington shows that even small areas of well-treated forest can reduce the intensity of fires and the damage to older trees.

Study suggests thinning, combined with fuels removals, could help make forests more resilient to climate change

By Bob Berwyn

SUMMIT COUNTY — Even small fuel treatments of only a few acres can help reduce wildfire severity and protect older trees desirable for timber, wildlife, and carbon-storage values, according to the results of a three-year study recently completed in Washington. Such treatments could also help make forests more resilient in the face of climate change, a team of university and Forest Service researchers concluded.

“If dense forests are thinned and the surface fuels are removed, then ponderosa pine and Douglas-fir trees have a better chance of surviving an intense wildfire,” said Susan Prichard, a University of Washington research scientist and senior author of the study conducted after the 175,000 acre Tripod Fire.

The joint University of Washington and U.S. Forest Service study was published in the August issue of Canadian Journal of Forest Research.

With a well-documented management history on the Okanogan-Wenatchee National Forest, Prichard and her Forest Service colleagues were able to compare fire effects in untreated stands, stands that were thinned, and stands that were thinned and then underwent prescribed burns to remove surface fuels.

In untreated and thinned stands, the Tripod Fire killed more than 80 percent of the trees. But in areas that were thinned and treated with controlled burns to remove surface fuels, only 40 percent of the trees were killed, and the treatments were especially helpful in preserving larger trees with diameters of eight inches or more.

“It’s all about fuels. Dead fuels on the ground add energy to wildfire and carry it across the landscape and dense stands of live trees and shrubs act as fuel ladders, moving fire into the canopy,” said Dave Peterson, a research biologist with the Forest Service’s Pacific Northwest Research Station who coauthored the study. “The objective of fuel treatments is not to eliminate wildfires, but to reduce their intensity in areas where we want to protect resources.”

If, as expected, a warmer climate causes an increase in wildfire in future decades, conducting fuel treatments in forest ecosystems will be an important tool for reducing damage from fire and increasing resilience to climate change.

“If we implement treatments across large areas and place them strategically, we can manage these low-elevation forests sustainably, even in a warmer climate,” Peterson said.


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